1. Field of the Invention
This invention relates to sulfur vulcanizable elastomer composites which are based upon vulcanizable unsaturated polymers and copolymers such as natural rubbers, polyisoprenes, polybutadienes, poly(butadiene-co-styrene), poly(butadiene-co-acrylontrile), poly(isobutylene-co-butadiene, and the like. More particularly, this invention relates to means for enhancing the coupling action, in such sulfur vulcanizable elastomers, of polysulfide alkoxy silane coupling agents.
2. Description of the Prior Art
Polysulfide alkoxy silane coupling agents are known, and are described e.g. in U.S. Pat. Nos. 3,842,111, 3,873,489, 4,003,843, and 4,044,037. Polysulfide-functional organosilanes are, like mercapto-functional organosilanes, useful as coupling agents in silica-filled and silicate-filled sulfur vulcanizable elastomer composites. However, the polysulfide-functional organosilanes are, as compared to the mercapto-functional organosilanes, less active. Under comparable conditions, the former produce lesser improvements than do the latter in elastomer vulcanizate properties such as tensile modulus.